Tuning indicator for radio receivers



1311.26, 1937. J. A. BRIGGS 2,069,131

1 TUNING INDICATOR FOR RADIO RECEIVERS Jan. 26, 1937. J. A. amass TUNING INDICATOR FOR RADIO RECEIVERS Filed April 27, 1956 4 Sheets-Sheet 2 Eweru? (JO Jan. 26, 1937. J. A. BRIGGS TUNING INDICATOR FOR RADIO RECEIVERS Filed April 27, 1936 4 Sheets-Sheet 3 I lnllllllllllllllmv Jan. 26, 1937. J. A. BRIGGS 2,059,131

TUNING INDICATOR FOR RADIO RECEIVERS Filed April 27, 1936 4 Sheets-Sheet 3 Jan. 26, 1937. J. A. BRIGGS TUNING INDICATOR FOR RADIO RECEIVERS Filed April 27, 1936 4 sheets-sheet 4 Patented Jan. 2 1931 UNITED STATES PATENT OFFlCE TUNING INDICATOR-FOR. nsnro nncsrvnas Joseph'A. Briggs, Erlton, N. 1., aslisnor to Philco Radio & Television Corporation, Philadelphia, Pa., a corporation of Delaware Application April 21, 1936, Serial No. 76,889

' 13 Claim- This invention relates to tuning indicators for radio receivers and the like apparatus, the principal object of the invention being to provide an improved device'of this class which is simple in construction,. efllcient in operation, and

adapted to perform the specifically set forth.

A more specific object of the invention is to I provide an improved tuning indicator device' wherein a light image is formed upon a dial and there is provided means for sharply defining the image and. for substantially eliminating background shadows.

Another object of the invention is to provide a simple and inexpensive means in theform of a light-transmitting cylindrical member arranged cooperatively with certain other elements of the device to effect the above-stated functions. Still another object of the invention is to provide a tuning indicator of this character which is,

I Fig. 3 is a fragmentary perspective view illustrating more clearly the elements of the device and their cooperative relation;

vice;

of Fig. 1; and

Fig. 6 is a diagrammatic illustration of the manner of operation of the device.

Referring particularly to Figs. 1 and 2 of the awings, a support i carries a frame 2 which, in turn, supports the usual variable tuning condensers 3 of the radio receiver, as well known. The rotatable shaft 4 of the tuning condenser assembly carries a gear 5 which meshes with a small gear 6 afllxed to the inner end of the manually operable shaft 1, the outer end of this shaft carrying a control knob 8. The tuning condenser shaft 4 also carries a gear 9 which meshes with a gear to rotatably mounted on a a stud ll secured to the front wall i2 of frame 2.

flinctions hereinafter Fig. 4 is a fragmentary face view of the dc Fig. 5 is a sectional view taken along line 5-K (c1. lie-1244) Y A hub structure It is secured to gear l0 so as to be rotatable therewith and carries a, translucent tuning dial ll. It will be seen. therefore, that rotation of the shaft 1 through the medium of control knob I rotates the tuning condenser 5 shaft 4 through gears i and 8 and also rotates the tuning dial ll through gears l and ID.

A bracket I! is supported by frame 2 and, in turn, supports a bracket it upon which there is mounted a lamp structure H. The lamp struco ture includes a reflector I 8 surrounding the lamp J9 so as to direct the light rays in a desired direction as will be more clearly understood later. The bracket I! carries a frame 20 having a window opening therein. as shown more clearly in 5 Fig. 3. A light-transmitting cylindrical'member v2i, which preferably takes the form of a glass rod, is disposed centrally of the frame 20 and carried thereby. To this end, there are provided on frame 20 upper and lower lugs 22 adapted to seat the member 21 and the said member is removably secured in place by means of resilient members 23, the ends of which are removably secured by lugs '24 provided on the frame 20. The members 22 may conveniently comprise pieces of resilient wire or the like. A translucent screen or plate 2 is also secured to the frame 20 and covers the window openings thereof, as clearly illustrated in Fig. 3 wherein the upper portion of the translucent screen is broken away for clarity of illustration. At its central portion, the translucent screen 25 is provided with a. slot-like aperture 28 which is axially aligned with the cylindrical member 2i. The aperture 2 constitutes an area of greater lighttransmitting characteristic than the remaining area of screen 25. While it is preferred to employ an aperture, it will be appreciated that. the screen may be formed of materials having different light-transmitting characteristics to provide the desired area, or other methods may be employed.

It will be seen that the translucent screen 25 is stationary and, as shown more clearly in Fig. 5, this screen is arranged behind the movable trans-. lucent dial it and the cylindrical member 2| is interposed between dial it and screen 25. It will also be seen that the screen 25 is interposed between dial it and the light source i9, and there is formed upon the translucent dial M a light image having the shape of a narrow line of light. This .light image is formed on dial 'H by means, first, of the greater light-transmitting charac- I teristic of the aperture 26 compared to the lighttransmitting characteristic of the remaining area 551 transmitted through the screen 25 and dial ll forms an illuminated background for the light image, the image being'distinctly brighter than the background. The cylindrical member 2| the medium of knob serves to more sharply define the light image and tosubstantially eliminate background shadows, as will be explained more fully hereinafter.

For use in multi-band receivers. of the type above mentioned, there is provided between the translucent screen 25 and the light source I!) a second translucent screen 2]. This second screen is carried'by a support 28 which is loosely mounted upon the hub of gear I, so that the support 28 and the screen 21 carried thereby are freely rotatable as a unit. The screen 21 is provided with arcuate openings 29, as shown in Fig. 3,. which are arranged cooperatively with the re-.

spective sets of graduations upon the dial ll shown clearly in Fig; 4. As will be well understood, the concentric sets of indicia or. graduations upon dial I4 designate different wave bands or frequency bands to. which the radio, receiver is receptive.- Although the screen 21 is broken away in Fig. 3 forclarity of illustration, it will be understood that there will be an aperture 29 for each of the different sets of indicia on dial M. It will be seen also that the apertures 29 are spaced from one another angularly and also radially, the radial spacing of these apertures corre-- sponding to the radial spacing ofthe sets of in.-

dicia on dial M. It will be seen, therefore, that by rotating the screen 2! any desired one of the apertures 29 may be brought into position behind the elongated slot 26'for use in conjunction with the corresponding set of indicia on dial l4 when it is desired to operate the receiver to receive broadcast signals within the particular frequency range or wave band. The aperture 29, which is thus positioned behind the elongated slot 26, defines a background area for the above-mentioned image, which area is more brilliantly illuminated than the remaining background area and stands out in contrast therewith bllt1lS less brilliantly illuminated than the image...formed by slot 26.

Moreover, the aperture 29 serves .to confine the indicating image to the'particular set of indicia on dial l4 being used in therparticular instance.

The support 28 has connected thereto a link til (see Fig. 1), the lower end, of which isconnected by a crank arm 3| to the front end of the rotatable shaft 32 forming a part of the wave band switch 33. As the wave; band switch is a conventional element of the multi-band receiver, it is unnecessary to illustrate or .describesuch device in detail, it being suflicient to note that this device-adapts the radio receiver for reception in any oneof the several frequency bands or wave bands and is actuated by rotation of the shaft 32. The shaft 321s manuallypperable by virtue of the control knob 34. It will be seen, however, that rotationof the shaft 32, through 34, in addition to actuating the wave band switch, rotates the .screen 21 through the medium of link 30, the parts being so arranged or designed that the aperture 29 corresponding to a particular position of the wave band switch is brought into position behindslot such as that of which the translucent dials of tuning devices for radio receivers are commonly made. Thesemembers may be readily cut or understood. .As stated above, the cylindrical member 2| may be formedof glass rod and may be simply cut from a length of rod of the desired diameter. 7

The operation of the device is illustrated diagrammatically in Fig. 6. In this illustration, the parts are greatly enlarged to illustrate the action more clearly. Light rays passing through the central part of slot 26 along the axiso will pass through the light-transmitting cylindrical memher and will converge or be brought to a focus upon the translucent dial I at point 1). Light rays passing through the slot 26 on opposite sides of the axis 0, such as those illustrated at a, b, c,

a, b and 0', will be bent upon passing into the cylindrical member 2|, as clearly illustrated, and upon leaving the member 2| will be further bent and will converge or be brought to a focus substantially at the point 1). Thus, the light rays which pass throughthe slot .26 are refracted and brought to a focus by the cylindrical member 2| in a line passing through point p and perpendicular to the plane of the paper as viewed in Fig. 6. In other words, these light rays will be brought to sharp focus in a line upon the translucent dial i4, so that a sharply defined line of light is formed upon the dial and the indicia on the. dial may be brought into accurate coincidence with this line-like image, thus enabling accurate and easy tuning of the receiver Light rays, such as those shown at d and d,

which pass through the screen 25 near'aperture 26 are refracted as illustrated and brought to a focus at point m spaced from point p. In like manner, light rays which are furtherremoved from slot 26, such as those illustrated at e and e, will be refracted and brought to a focus at a point n still further removed from point p. These light rays, however, will impinge upon the dial I4 and will forni a substantially shadowless background for the sharply defined image above mentioned.

In general, light rays entering the cylindrical member on a path parallel to the axis will come to a focus at a point on the axis which will depend upon the distance between the path of the incoming ray and the axis. Where this distance is small, that is, where the ray path is close to the axis, the ray. will come to a focus or cross the axis at a point dependent largely upon the index of refraction of the focusing member, the point being one-half the radius away from the surface of the cylindrical member for the case in which the index of refraction of the member is 1".50 which is the approximate value for common glass. Rays entering the rod parallel to the axis but a greater distance away from it will cross the axis on the other-side at a point nearer the surface, the distance of thispoint from the surface being nearly one-half the radius for a glass rod in the casein which the distance of the incoming rays from the axis is less than one-half the radius of the rod, such as rays a, b, and c, while for rays such as d, e for whichthe latter distance is'greater than'one-half the rod radius. the distance between the intersection of the ray with the axis and the surface of the rod will be considerably less than one-half the rod radius.

Advantage istaken of this peculiar focusing characteristic of a cylindrical rod to form the desired line of light without the usual shadow formedby light focusing means. By positioning the translucent dial, at a point slightly less than one-half the rod radius from the surface of the stamped from sheets of material, as will be well i about one-half the rod radius from the axis is made to converge upon a narrow line on the dial member and thus serves to define a sharp line of light thereon. Now light passing through the translucent screen 25 away from the rod; such as my I, will be diffused and broken up by the screen to form rays, such as g, h,'7', is, Z which serve to illuminate the dial l4 generally. These rays will, of course, be considerably diminished in intensity due to the poor light transmission properties of the translucent screen. These rays serve to form the general illumination of the whole window as indicated by the dotted line in Fig. 4. It will be seen, however, that the rod would tend to cast a shadow upon the dial l4 between the generally illuminated area and the bright line of light except for the peculiar focusing action of the rod which causes rays such as d-and e toconverge more completely and thus impinge on the dial in this inbetween region. This eil'ect is further augmented by the fact that light passing through the screen 25 is diffused, and thus rays such as d and e will be-modifled in passing through the screen and will enter the rod along several diflferent directions as shown in Fig. 6. For the sake of simplicity,-only one path ((1, e) ,is shown for each ray diffused by the screen 25, but it will be understood that I the other diffused rays will pass through the rod,

passing through the aperture 26 do so along paths be refracted as indicated by other rays, and eventually impinge on the dial Hi.

It will be noted that the width of the aperture 26 will not have mucheffect upon the width of the light image, but simply serves to control the total amount of light which is brought to the sharp focus. The width of the light image is determined by the distance of the dial from the rod, and as indicated, the narrowest line may be obtained when the dial is positioned slightly less than one-half the rod radius from the surface of the rod. As described more clearly'below, the invention provides means for holding the dial in this preferred position as the dial itself is moved.

In the above discussion no mention has been made of the screen 21. Where light passes through an aperture 29 in the screen 21, the focusing of the lightrby the several means will be as described and a short bright line of light formed as indicated in Fig. 4. Light passing through the translucent screen 21 rather than through an aperture in the screen will, however, be diminished in intensity and will further be diffused by the screen. Thus, an area generally similar to the aperture 29 will be outlined on the dial as indicated in Fig. 4. Now the focusing action of the rod depends upon having the light generally parallel to the axis (Fig. 6), and while this requirement is not sufficiently critical to make it necessary to put the light source in any one particular spot, nevertheless, the screen 21 will sufliciently difiuse the light so that light passing through this screen will not be brought to a focus by the other means and thus the length of the line of light on the dial M will be determined by the width ofthe aperture 29 through which light is transmitted to the rod and screen 25 and by proper design this line of light may be arranged to cover only one wave band on the dial, and a section of this band on each side I of the line of light may be illuminated somewhat more brightly than the remaining area, as indicated in Fig. 4. It is worthy of note that as the large portion of light transmitted through the dial I4 is of diffused character, the general apreceiver without irritation to his eyes.

Thus, the cylindrical member 2|, in cooperative arrangement with the slotted screen 25, serves to produce a sharply defined image on dial l and also serves to substantially eliminate shadows -from the background surrounding the image. It will be understood, of course, that the member 2| should be properly related in diameter to the width of slot 26, but these dimensions may vary somewhat relative to one another. Preferably, the slot 2'6 should not be greater in width than the radius of the cylindrical member 2|. The index of refraction of material of which the member 2| is formed will, of course, have a bearing upon the functioning of the device but, in general, any common glass or similar material may be used. It will be understood, of course, that the invention is not limited to the dimensions or materials herein specifically mentioned, as it is possible to design the device to obtain varying efiects.

In order to maintain the dial M in proper relation to the member 2|, there are provided on the frame 20 support and guide projections 35 having raised nubs 3B thereon (see Figs. 3 and 4) which projections extend around the edge of the dial to the front thereof, and there are also provided on frame 2|] nubs 31 (see Figs. 1 and 4) disposed behind the dial. The front nubs 36 and the rear nubs 31 thus seat and guide the portion of dial l4 adjacent frame 20 and maintain that portion of the dial parallel to and in fixed relation with the axis of member 2|. Moreover, this light-receiving portion of the dial is thus kept fiat and presents a uniform surface to the light passing through screens and 21.

From the illustration and above description, it will be seen that the device provided by the invention is of simple construction'and may be economically manufactured, and it will also be seen that it embodies a novel combination or arrangement of parts which serve cooperatively to produce asharp line-like image upon the indicator dial with a substantially shadowless background for the image. It will be understood, of course, that the invention is not limited to the specific form illustrated and that various changes and modifications may be made without departing from the scope of the invention as defined by the appended claims.

I claim:

1. A tuning indicator for radio receivers or the like, comprising a movable translucent dial having indicia thereon, a source of light, a translucent screen interposed between said dial and said light source, said screen having an area of different light-transmitting characteristic from the remaining area of the screen, and focusing means cooperatively. associated with said area for producing a sharply defined image upon said dial with which said indicia may be made to coincide by moving said dial.

light source, said screen having an area of different light-transmitting characteristic from the remaining area of the screen, and focusing means interposed between said screen and said dial, adjacent said area and the portion of said screen thereabout, for producing a sharply defined image upon said dial with which said indicia may be made to coincide by moving said dial and for substantially eliminating background shadows.

3. A tuning indicator for radio receivers or the like, comprising a movable translucent dial having indicia thereon, a source of light, a translucent screen interposed between said'dial and said light source, said screen having an elongated area of different light-transmitting characteristic from the remaining area of the screen, and a light-transmitting member having opposed cylindrical surfaces, cooperatively associated and axially aligned with said area, for producing a sharply defined image upon said dial with which said indicia'may be made to coincide by moving said dial.

4. A tuning indicator for radio receivers or the like, comprising a movable translucent dial having indicia thereon, a source of light, a translucent screen interposed between said dial and said light source, said screen having an elongated area of diiferent light-transmitting characteristic from the remaining area of the screen, and a light-transmitting cylindrical member, cooperatively associated and axially aligned with said area, for producing a sharply defined image upon said dial with which said indica may be made to coincide by moving said dial.

5. A tuning indicator for radio receivers or the like, comprising a movable translucent dial having indicia thereon, asource of light, a translucent screen interposed between said dial and said light source, said screen having an elongated area of different light-transmitting characteristic from the remaining area of the screen, and a lighttransmitting cylindrical member interposed between said screen and said dial, and axially aligned with said'area and the portion of said screen thereabout, for producing a sharply defined image with which said indicia may be made to coincide by moving said dial and for substantially eliminating background shadows.

6. A tuning indicator for radio receivers or the' like, comprising a movable translucentdial ha;v

ingindicia thereon, a source of light, a translucent screen interposed between said dial and said light source, said screenhaving an elongated area of different light-transmitting characteristic from the remaining area of the screen, and a light-transmitting cylindrical member interposed between said screen and said dial, and axially aligned with said'area and the portion of said screen thereabout, for producing a sharply defined image upon said dial with which said indicia may be made to coincide by moving said dial and for substantially eliminating back.-

ground shadows, said member having a diameter at least twice as great as the width of said area. 7. A tuning indicator for radio receivers or the like, comprising a movable translucent dial having indicia thereon, a source of light, a supporting frame interposed between said dial and said light source, a' translucent screen carried by said frame, said screen having an area of different light-transmitting characteristic from the remaining area of the screen, and a lighttransmitting member carried by said frame in cooperative. association with said area for pro ducing a sharply defined image upon said dial with which said indicia may be made to. coincide by moving said dial.

8. A tuningindicator for radio receivers or the like, comprising a movable translucent dial having indicia thereon, a source of light, a translucent screen interposed between said dial and said light source, said-screen having an area of y different light-transmitting characteristic from the remaining area of the screen, a light-transmitting member cooperatively associated with said area for producing a sharply defined image upon said dial with which said indicia may be made to coincide by moving said dial, and

means for maintaining said dial'in proper relation to said member.

9. A tuning indicator for radio receivers or the like, comprising a movable translucent dial having indicia thereon, a source of light, a supporting frame interposed between said dial and said light source, a translucent screen carried by said frame, said screen having an area of different light-transmitting characteristic from the remaining area ofthe screen, a light-transmitting member carried by said frame in cooperative association with said area for producing a sharply defined image upon said dial with which said indicia may be made to coincide bymoving said dial, and means on said frame for maintaining said dial in proper relation to said member.

10. A tuning indicator for radio receivers or the like, comprising a movable translucent dial having indicia thereon, a source of light, a supporting frame interposed between said dial and said light source, a translucent screen carried by said frame, said screen having an area of different light-transmitting characteristic from the remaining area of the screen, a light-transmitting member carried by said frame in cooperative association with said area for producing a sharply defined image upon said dial with which said indicia may be made to coincide'by moving said dial, and a plurality of nubs on said frame on opposite sides-of said dial for maintaining said dial in proper relation to said mem- 'ber.

of light, a translucent screen interposed'between said dial and said light source, said screen having an elongated area of different light-transmitting characteristic from the remaining area of the screen, a movable translucent screen also interposed between said dial and said light source, and having spaced areas of diiferent light-transmitting characteristic from the remaining area of the screen, said areas corresponding respectively to said different sets of indicia and being adapted to be brought into cooperative relation with said elongated area by moving said last-mentioned screen, and focusing means cooperatively associated with said elongated area for producing a sharply defined image upon said dial with which said indicia may be made to coincide by moving said dial.

12. A tuning indicator for a multi-band radio receiver, comprising a movable translucent dial having different sets of indicia thereon, a source 7 indicia and being adapted to be brought into cooperative relation with said elongated area by sponding respectively to said different sets of moving said last-mentioned screen, and a lightis transmitting member having opposed cylindrical surfaces, cooperatively associated and axially aligned with said elongated area, for producing a sharply defined image upon said dial with which said indicia may be made to coincide by moving said dial.

13. A tuning indicator for a multi-band radio receiver, comprising a movable'translucent-dial having diiierent sets of indicia thereon, a source of. light, a translucent screen interposed between said dial and said light source, said screen having an elongated area of diflerent light-transmitting characteristic from the-remaining area of the screen, a translucent screen also inter posed between said dial and saidlight source,

and having spaced areas of different light-transmittingcharacteristic from the remaining area of the screen, saidareas corresponding respectively to said difierent sets of indicia and being adapted to be brought into cooperative relation with said elongated area by moving said last-mentioned screen, and a light-transmitting cylindrical member, cooperatively associated and axially aligned with said elongated area and the portion of said first screen thereabout, for producing a sharply defined image upon said dial with which said indicia may be made to coincide by moving said dial and for substantially eliminating background shadows.

JOSEPH A. BRIGGS. 

